Multi-tenant aware dynamic host configuration protocol (dhcp) mechanism for cloud networking

ABSTRACT

An approach includes providing support multi-tenancy support on a DHCP protocol. The approach includes receiving a dynamic host configuration protocol (DHCP) packet, inserting a tenant-specific option information within the DHCP packet, and transmitting the DHCP packet with the tenant-specific option information.

TECHNICAL FIELD

The technical character of the present invention generally relates to aDynamic Host Configuration Protocol (DHCP) mechanism for a cloudnetworking, and more particularly, to a DHCP mechanism for multi-tenantcloud networking.

BACKGROUND

Multi-tenant support is a basic demand for cloud data center networks,which requires service isolations between different tenants. One type ofservice isolation is address isolation which provides overlappingaddresses to different tenants. In current standards, such as InternetEngineering Task Force Network Virtualization Overlays (IETF NVO3)standards, a virtual network identifier (VNID) is provided to supportthe separation of virtual networks of different tenants in overlayvirtual networks. Addressing and host configuration can be providedthrough Dynamic Host Configuration Protocol (DHCP), which providesconfiguration parameters to hosts.

DHCP has two components, including a protocol for deliveringhost-specific configuration parameters from a DHCP server to a host anda mechanism for allocation of network addresses to hosts. In DHCP, theprotocol only supports a configuration in a single address space.Therefore, each DHCP server can only be configured with configurationparameters of a single address space (i.e., the protocol cannot supportoverlapped address spaces). Thus, the client of the DHCP server can onlyobtain an address from this single address space.

In order to provide overlapping addresses to different tenants in clouddata center networks, separate DHCP servers must be set up for eachtenant. This is usually implemented by setting up a unique DHCP serverin a separate LINUX namespace (i.e., operating system levelvirtualization) or running multiple DHCP servers in different hosts. Inthese implementations, there is one DHCP server for a tenant, and theaddresses provided to different tenants can be overlapped.

However, configuring multiple Linux namespaces is complex andresource/computation intensive since there is usually only one physicalnetwork interface card used to connect to the data network. Further,multiple Linux namespaces requires multiple virtual network interfacesto be created and connected to an Ethernet bridge to serve thosenamespaces and multiple DHCP server instances to be run in which eachone of them only serves a single tenant or even a single networksegment. Also, there is a lack of scalability when a number of tenantsgrow into the thousands. Further, many legacy operating systems (e.g.,WINDOWS SERVER and legacy LINUX kernels before 2.6.32.xx) do not supportLINUX namespaces.

Moreover, there is no inter-operability between overlay networks, evenwhen using overlay encapsulation protocols for multi-tenant support,such as virtual local area network (VLAN), virtual extensible local areanetwork (VXLAN), distributed overlay virtual Ethernet (DOVE), networkvirtualization using generic routing encapsulation (NVGRE), statelesstransport tunneling (STT), generic network virtualization encapsulation(GENEVE), etc. Therefore, such systems do not provide the flexibilityrequired for multi-tenant support.

SUMMARY

In a first aspect of the invention, a method is provided for thatincludes receiving a dynamic host configuration protocol (DHCP) packet.The method further includes inserting a tenant-specific optioninformation within the DHCP packet. The method further includestransmitting the DHCP packet with the tenant-specific optioninformation.

In another aspect of the invention, there is a computer program productthat includes a computer readable storage medium having program codeembodied in the storage medium. The program code is not a transitorysignal per se, and the program instructions are readable by a computingdevice to cause the computing device to perform a method that includesreceiving a dynamic host configuration protocol (DHCP) packet. Themethod further includes determining that the DHCP packet comprisestenant-specific option information. The method further includesselecting an address space based on the tenant-specific optioninformation.

In a further aspect of the invention, there is a computer program thatincludes a computer readable storage medium having program code embodiedin the storage medium. The program code is not a transitory signal perse, and the program instructions are readable by a computing device tocause the computing device to perform a method that includes receiving adynamic host configuration protocol (DHCP) packet which comprises atenant-specific option information. The method further includes locatinga tenant address space based on the tenant-specific option information.The method further includes obtaining a virtual network identifier froma virtual access point (VAP). The method further includes obtaining asubnet configuration corresponding to the obtained virtual networkidentifier. The method further includes allocating an internet protocol(IP) address which corresponds to the obtained subnet configuration.

In another aspect of the invention, a system is provided that includes aCPU, a computer readable memory, and a computer readable storage medium.Additionally, the system includes one or more program instructions. Thesystem includes program instructions to insert multi-tenancy informationwithin a dynamic host configuration protocol (DHCP) packet. The systemfurther includes program instructions to transmit the DHCP packet withthe multi-tenancy information. The program instructions are stored onthe computer readable storage medium for execution by the CPU via thecomputer readable memory.

In another aspect of the invention, a method is provided for configuringa tenant-specific DHCP option frame format that includes configuring afirst field of the tenant-specific DHCP option frame format to denote anoverlay protocol type that is used for tenant isolation. The methodfurther includes configuring a second field of the tenant-specific DHCPoption frame format to uniquely identify a tenant. The method furtherincludes configuring a third field of the tenant-specific DHCP optionframe format to denote a virtual network.

Embodiments of the present invention provide systems and methods thatimplement technical features such as a novel DHCP mechanism formulti-tenant cloud networking, which addresses the issue of addressisolation for different tenants in a more efficient manner than currentsystems. For example, in embodiments of the DHCP mechanism,tenant-specific information is included in a DHCP packet for a scopingof address space. The advantage of the aforementioned technical solutionfor embodiments of the DHCP mechanism is that it isbackwards-compatible, and does not adversely affect currentlyimplemented systems of DHCP processing. Further, if the tenant-specificinformation is not provided in the DHCP packet, DHCP processing canoccur in a manner as current systems. Moreover, in comparison to anaddress range in the DHCP packet which has a global scope, in thetechnical features of embodiments of the DHCP mechanism, the addressrange in the DHCP packet is scoped locally to a tenant's address spacewhen using the DHCP tenant-specific information.

Also, when using the DHCP mechanism of embodiments of the presentinvention, a single DHCP server is capable of providing DHCP servicesfor multiple tenants, even though their address range may overlap witheach other. Thus, in contrast to current systems, there is no need foroperating system (OS) level isolation (e.g., LINUX namespace). Further,embodiments of the DHCP mechanism simplify the DHCP service provisioningin multi-tenant cloud data centers. The technical features ofembodiments of the DHCP mechanism also address the interoperabilityissue when a data center network comprises heterogeneous virtualenvironments offered by different vendors.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is described in the detailed description whichfollows, in reference to the noted plurality of drawings by way ofnon-limiting examples of exemplary embodiments of the present invention.

FIG. 1 depicts a cloud computing node according to an embodiment of thepresent invention.

FIG. 2 depicts a cloud computing environment according to embodiments ofthe present invention.

FIG. 3 depicts abstraction model layers according to embodiments of thepresent invention.

FIG. 4 depicts a cloud computing note according to another embodiment ofthe present invention.

FIG. 5 is a frame format for a tenant-specific DHCP option in accordancewith aspects of the present invention.

FIG. 6 depicts an exemplary flow (swim diagram) for a DHCP packetprocessing in accordance with aspects of the present invention.

FIG. 7 depicts an exemplary flow for an address allocation processing inaccordance with aspects of the present invention.

FIG. 8 depicts an exemplary flow for a DHCP subnet selection support inaccordance with aspects of the present invention.

DETAILED DESCRIPTION

The technical character of the present invention generally relates to aDynamic Host Configuration Protocol (DHCP) mechanism for a cloudnetworking, and more particularly, to a DHCP mechanism for multi-tenantcloud networking. More specifically, embodiments of the presentinvention provide systems and methods that implement technical featuressuch as a novel DHCP mechanism for multi-tenant cloud networking, whichaddresses the issue of address isolation for different tenants in a moreefficient manner than current systems. For example, in embodiments ofthe DHCP mechanism, tenant-specific information is included in a DHCPpacket for a scoping of address space.

The advantage of the aforementioned technical solution for embodimentsof the DHCP mechanism is that it is backwards-compatible, and does notadversely affect currently implemented systems of DHCP processing.Further, if the tenant-specific information is not provided in the DHCPpacket, DHCP processing can occur in a manner as current systems.Moreover, in comparison to an address range in the DHCP packet which hasa global scope, in the technical features of embodiments of the DHCPmechanism, the address range in the DHCP packet is scoped locally to atenant's address space when using the DHCP tenant-specific information.

Also, when using the DHCP mechanism of embodiments of the presentinvention, a single DHCP server is capable of providing DHCP servicesfor multiple tenants, even though their address range may overlap witheach other. Thus, in contrast to current systems, there is no need foroperating system (OS) level isolation (e.g., LINUX namespace). Further,embodiments of the DHCP mechanism simplify the DHCP service provisioningin multi-tenant cloud data centers. The technical features ofembodiments of the DHCP mechanism also address the interoperabilityissue when a data center network comprises heterogeneous virtualenvironments offered by different vendors.

In further embodiments of the DHCP mechanism, a single DHCP serverproviding addressing service is used for multiple tenants in a clouddata center based on overlay networks. Embodiments of the DHCP mechanismhelp to solve the following technical issues in DHCP systems:

-   -   (i) Address space isolation for different tenants in the        presence of a DHCP relay agent;    -   (ii) Address subnet selection for tenant virtual networks with        the aid of Network Virtualization Authority (NVA); and    -   (iii) General DHCP service provisioning for heterogeneous        virtual environments that comprise a legacy physical        infrastructure network and overlay networks with different        encapsulation protocols (VLAN, VXLAN, NVGRE, STT, or GENEVE).

Further, embodiments of the DHCP mechanism do not disrupt current DHCPinteractions between clients and a server, such as DHCP DISCOVER, OFFER,REQUEST, ACKNOWLEDGMENT, RELEASE, etc. In fact, the DHCP interactionsalso work in embodiments of the DHCP mechanism of the present invention.

In additional technical features of embodiments of the DHCP mechanism,the tenant-specific option is used as an indicator for a DHCP server toallocate an internet protocol (IP) address on an associated addressspace specific to that tenant. Hence, a single DHCP server can serve aplurality of tenants, and each tenant can have its own IP address poolfor allocation. Moreover, each pool in a tenant is totally independentand can be overlapped (i.e., same IP address pool) with another pool fora different tenant. The tenant-specific option is added to a DHCP headerby a DHCP relay agent.

In the technical solutions of the present invention, the tenant-specificoption comprises the following fields:

-   -   (i) option: should have a unique value, used in known DHCP        systems;    -   (ii) length: total number of bytes of remaining fields;    -   (iii) transport agent: encoding value to denote the overlay        protocol type that is used for tenant isolation (e.g., VLAN,        VXLAN, DOVE, NVGRE, STT, etc.);    -   (iv) tenant ID: a universally unique identifier (UUID) used to        identify a tenant; and    -   (v) virtual network ID (VNID): denotes a virtual network, which        is an abstract of a L2 segment or broadcast domain. A tenant may        have multiple virtual networks.

In further embodiments, the tenant specific option is implemented as asub-option in a DHCP relay agent information option (option 82, RFC3046). In embodiments, the implementation adds a sub-option in theoption 82 standard to include the proposed tenant-specific option. Thetenant-specific option is added to the DHCP header by a DHCP relayagent, which runs on a network virtualization edge (NVE). Since the NVEis on an edge of the overlay network, it is easy to derive the encodingvalue of a transport agent in the tenant specific option. For example,the VNID can be derived from a virtual access point (VAP) on which theDHCP client connects.

In order to enable multi-tenant support in embodiments of the DHCPmechanism, the DHCP server supports two types of address spaces: globaladdress space and tenant address space. The global address space iscompatible with a known DHCP mechanism in which a tenant-specific optionis not present in the DHCP packet. In the global address space of acurrent DHCP mechanism, the IP address ranges cannot be overlapped;whereas, in the technical solution using embodiments of the DHCPmechanism of the present invention, each tenant has a specific addresspool in the tenant address space, and the address range in the DHCPmechanism can be overlapped across different tenant's address pool.

In embodiments of the DHCP mechanism, if the DHCP_DISCOVER message doesnot include the tenant specific option, a DHCP server performs a knownDHCP processing. Otherwise, if the DHCP_DISCOVER message includes thetenant specific option, the tenant specific option is used to locate thetenant address space and IP range. The DHCP server locates the addressspace corresponding to the tenant ID in the tenant-specific option. Ifthe DHCP_DISCOVER message has a subnet selection option (option 118) ora link selection sub-option (sub-option 5 in option 82), the DHCP serverwill allocate an address from that subnet. Otherwise, if theDHCP_DISCOVER message does not have a subnet selection option or a linkselection sub-option, an IP range is associated to a VNID, and the DHCPserver will find the IP range according to the VNID in the tenantspecific option. Further, embodiments of the DHCP mechanism of thepresent invention can include a DHCP server which uses a matchingcriteria or access control list (ACL) rules on the tenant-specificoption in the configuration to locate the tenant address space.

In embodiments of the DHCP mechanism of the present invention, a cloudservice provider (CSP) may employ various overlay network solutions fromdifferent vendors to achieve a multi-tenant cloud data center.Therefore, embodiments of the DHCP mechanism can be utilized when thenetwork size is expanded. In an example, the CSP may have two overlaynetworks, and these overlay networks may be built on top of a commonphysical network. A tenant may have virtual machines in both overlaynetworks. Therefore, in embodiments of the novel DHCP mechanism, thereis a convenient way to provision the DHCP server in the physical networkin case of a tenant having virtual machines spanning acrossheterogeneous overlay networks. The transport agent field in a tenantspecific option is used to provision the DHCP server.

As the scope of VNID is limited to a single overlay network, in suchheterogeneous networks, the DHCP server in embodiments of the DHCPmechanism can use the transport agent, together with VNID, in the tenantspecific option, as the classification fields to derive the IP rangefrom which IP addresses are allocated. Thus, to achieve IP addressmanagement service for heterogeneous virtual overlay networks with asingle DHCP server in a cloud data center, a transport agent may beadded as a dimension in the classification criteria to locate the IPaddress range in the tenant address space.

It is understood in advance that although this disclosure includes adetailed description on cloud computing, implementation of thetechniques recited herein are not limited to a cloud computingenvironment. Rather, embodiments of the present invention are capable ofbeing implemented in conjunction with any other type of computingenvironment now known or later developed.

Cloud computing is a model of service delivery for enabling convenient,on-demand network access to a shared pool of configurable computingresources (e.g. networks, network bandwidth, servers, processing,memory, storage, applications, virtual machines, and services) that canbe rapidly provisioned and released with minimal management effort orinteraction with a provider of the service. This cloud model may includeat least five characteristics, at least three service models, and atleast four deployment models.

Characteristics are as follows:

On-demand self-service: a cloud consumer can unilaterally provisioncomputing capabilities, such as server time and network storage, asneeded automatically without requiring human interaction with theservice's provider.

Broad network access: capabilities are available over a network andaccessed through standard mechanisms that promote use by heterogeneousthin or thick client platforms (e.g., mobile phones, laptops, and PDAs).

Resource pooling: the provider's computing resources are pooled to servemultiple consumers using a multi-tenant model, with different physicaland virtual resources dynamically assigned and reassigned according todemand. There is a sense of location independence in that the consumergenerally has no control or knowledge over the exact location of theprovided resources but may be able to specify location at a higher levelof abstraction (e.g., country, state, or datacenter).

Rapid elasticity: capabilities can be rapidly and elasticallyprovisioned, in some cases automatically, to quickly scale out andrapidly released to quickly scale in. To the consumer, the capabilitiesavailable for provisioning often appear to be unlimited and can bepurchased in any quantity at any time.

Measured service: cloud systems automatically control and optimizeresource use by leveraging a metering capability at some level ofabstraction appropriate to the type of service (e.g., storage,processing, bandwidth, and active user accounts). Resource usage can bemonitored, controlled, and reported providing transparency for both theprovider and consumer of the utilized service.

Service Models are as follows:

Software as a Service (SaaS): the capability provided to the consumer isto use the provider's applications running on a cloud infrastructure.The applications are accessible from various client devices through athin client interface such as a web browser (e.g., web-based e-mail).The consumer does not manage or control the underlying cloudinfrastructure including network, servers, operating systems, storage,or even individual application capabilities, with the possible exceptionof limited user-specific application configuration settings.

Platform as a Service (PaaS): the capability provided to the consumer isto deploy onto the cloud infrastructure consumer-created or acquiredapplications created using programming languages and tools supported bythe provider. The consumer does not manage or control the underlyingcloud infrastructure including networks, servers, operating systems, orstorage, but has control over the deployed applications and possiblyapplication hosting environment configurations.

Infrastructure as a Service (IaaS): the capability provided to theconsumer is to provision processing, storage, networks, and otherfundamental computing resources where the consumer is able to deploy andrun arbitrary software, which can include operating systems andapplications. The consumer does not manage or control the underlyingcloud infrastructure but has control over operating systems, storage,deployed applications, and possibly limited control of select networkingcomponents (e.g., host firewalls).

Deployment Models are as follows:

Private cloud: the cloud infrastructure is operated solely for anorganization. It may be managed by the organization or a third party andmay exist on-premises or off-premises.

Community cloud: the cloud infrastructure is shared by severalorganizations and supports a specific community that has shared concerns(e.g., mission, security requirements, policy, and complianceconsiderations). It may be managed by the organizations or a third partyand may exist on-premises or off-premises.

Public cloud: the cloud infrastructure is made available to the generalpublic or a large industry group and is owned by an organization sellingcloud services.

Hybrid cloud: the cloud infrastructure is a composition of two or moreclouds (private, community, or public) that remain unique entities butare bound together by standardized or proprietary technology thatenables data and application portability (e.g., cloud bursting forload-balancing between clouds).

A cloud computing environment is service oriented with a focus onstatelessness, low coupling, modularity, and semantic interoperability.At the heart of cloud computing is an infrastructure comprising anetwork of interconnected nodes.

Referring now to FIG. 1, a schematic of an example of a cloud computingnode is shown. Cloud computing node 10 is only one example of a suitablecloud computing node and is not intended to suggest any limitation as tothe scope of use or functionality of embodiments of the inventiondescribed herein. Regardless, cloud computing node 10 is capable ofbeing implemented and/or performing any of the functionality set forthhereinabove.

In cloud computing node 10 there is a computer system/server 12, whichis operational with numerous other general purpose or special purposecomputing system environments or configurations. Examples of well-knowncomputing systems, environments, and/or configurations that may besuitable for use with computer system/server 12 include, but are notlimited to, personal computer systems, server computer systems, thinclients, thick clients, hand-held or laptop devices, multiprocessorsystems, microprocessor-based systems, set top boxes, programmableconsumer electronics, network PCs, minicomputer systems, mainframecomputer systems, and distributed cloud computing environments thatinclude any of the above systems or devices, and the like.

Computer system/server 12 may be described in the general context ofcomputer system-executable instructions, such as program modules, beingexecuted by a computer system. Generally, program modules may includeroutines, programs, objects, components, logic, data structures, and soon that perform particular tasks or implement particular abstract datatypes. Computer system/server 12 may be practiced in distributed cloudcomputing environments where tasks are performed by remote processingdevices that are linked through a communications network. In adistributed cloud computing environment, program modules may be locatedin both local and remote computer system storage media including memorystorage devices.

As shown in FIG. 1, computer system/server 12 in cloud computing node 10is shown in the form of a general-purpose computing device. Thecomponents of computer system/server 12 may include, but are not limitedto, one or more processors or processing units 16, a system memory 28,and a bus 18 that couples various system components including systemmemory 28 to processor 16.

Bus 18 represents one or more of any of several types of bus structures,including a memory bus or memory controller, a peripheral bus, anaccelerated graphics port, and a processor or local bus using any of avariety of bus architectures. By way of example, and not limitation,such architectures include Industry Standard Architecture (ISA) bus,Micro Channel Architecture (MCA) bus, Enhanced ISA (EISA) bus, VideoElectronics Standards Association (VESA) local bus, and PeripheralComponent Interconnects (PCI) bus.

Computer system/server 12 typically includes a variety of computersystem readable media. Such media may be any available media that isaccessible by computer system/server 12, and it includes both volatileand non-volatile media, removable and non-removable media.

System memory 28 can include computer system readable media in the formof volatile memory, such as random access memory (RAM) 30 and/or cachememory 32. Computer system/server 12 may further include otherremovable/non-removable, volatile/non-volatile computer system storagemedia. By way of example only, storage system 34 can be provided forreading from and writing to a non-removable, non-volatile magnetic media(not shown and typically called a “hard drive”). Although not shown, amagnetic disk drive for reading from and writing to a removable,non-volatile magnetic disk (e.g., a “floppy disk”), and an optical diskdrive for reading from or writing to a removable, non-volatile opticaldisk such as a CD-ROM, DVD-ROM or other optical media can be provided.In such instances, each can be connected to bus 18 by one or more datamedia interfaces. As will be further depicted and described below,memory 28 may include at least one program product having a set (e.g.,at least one) of program modules that are configured to carry out thefunctions of embodiments of the invention.

Program/utility 40, having a set (at least one) of program modules 42,may be stored in memory 28 by way of example, and not limitation, aswell as an operating system, one or more application programs, otherprogram modules, and program data. Each of the operating system, one ormore application programs, other program modules, and program data orsome combination thereof, may include an implementation of a networkingenvironment.

Program modules 42 generally carry out the functions and/ormethodologies of embodiments of the invention as described herein. Forexample, some or all of the functions of a DHCP client 80 can beimplemented as one or more of the program modules 42. Additionally, theDHCP client 80 may be implemented as separate dedicated processors or asingle or several processors to provide the functionality describedherein. In embodiments, the DHCP client 80 performs one or more of theprocesses described herein.

Computer system/server 12 may also communicate with one or more externaldevices 14 such as a keyboard, a pointing device, a display 24, etc.;one or more devices that enable a user to interact with computersystem/server 12; and/or any devices (e.g., network card, modem, etc.)that enable computer system/server 12 to communicate with one or moreother computing devices. Such communication can occur via I/O interfaces22. Still yet, computer system/server 12 can communicate with one ormore networks such as a local area network (LAN), a general wide areanetwork (WAN), and/or a public network (e.g., the Internet) via networkadapter 20. As depicted, network adapter 20 communicates with the othercomponents of computer system/server 12 via bus 18. It should beunderstood that although not shown, other hardware and/or softwarecomponents could be used in conjunction with computer system/server 12.Examples, include, but are not limited to: microcode, device drivers,redundant processing units, external disk drive arrays, RAID (redundantarray of inexpensive disks or redundant array of independent disks)systems, tape drives, and data archival storage systems, etc.

Referring now to FIG. 2, illustrative cloud computing environment 50 isdepicted. As shown, cloud computing environment 50 comprises one or morecloud computing nodes 10 with which local computing devices used bycloud consumers, such as, for example, personal digital assistant (PDA)or cellular telephone 54A, desktop computer 54B, laptop computer 54C,and/or automobile computer system 54N may communicate. Nodes 10 maycommunicate with one another. They may be grouped (not shown) physicallyor virtually, in one or more networks, such as Private, Community,Public, or Hybrid clouds as described hereinabove, or a combinationthereof. This allows cloud computing environment 50 to offerinfrastructure, platforms and/or software as services for which a cloudconsumer does not need to maintain resources on a local computingdevice. It is understood that the types of computing devices 54A-N shownin FIG. 2 are intended to be illustrative only and that computing nodes10 and cloud computing environment 50 can communicate with any type ofcomputerized device over any type of network and/or network addressableconnection (e.g., using a web browser).

Referring now to FIG. 3, a set of functional abstraction layers providedby cloud computing environment 50 (FIG. 2) is shown. It should beunderstood in advance that the components, layers, and functions shownin FIG. 3 are intended to be illustrative only and embodiments of theinvention are not limited thereto. As depicted, the following layers andcorresponding functions are provided:

Hardware and software layer 60 includes hardware and softwarecomponents. Examples of hardware components include mainframes 61; RISC(Reduced Instruction Set Computer) architecture based servers 62;servers 63; blade servers 64; storage device 65; and networks andnetworking components 66. In some embodiments, software componentsinclude network application server software 67 and database software 68.

Virtualization layer 70 provides an abstraction layer from which thefollowing examples of virtual entities may be provided: virtual servers71; virtual storage 72; virtual networks 73, including virtual privatenetworks; virtual applications and operating systems 74; and virtualclients 75.

In one example, management layer 80 may provide the functions describedbelow. Resource provisioning 81 provides dynamic procurement ofcomputing resources and other resources that are utilized to performtasks within the cloud computing environment. Metering and Pricing 82provide cost tracking as resources are utilized within the cloudcomputing environment, and billing or invoicing for consumption of theseresources. In one example, these resources may comprise applicationsoftware licenses. Security provides identity verification for cloudconsumers and tasks, as well as protection for data and other resources.User portal 83 provides access to the cloud computing environment forconsumers and system administrators. Service level management 84provides cloud computing resource allocation and management such thatrequired service levels are met. Service Level Agreement (SLA) planningand fulfillment 85 provide pre-arrangement for, and procurement of,cloud computing resources for which a future requirement is anticipatedin accordance with an SLA.

Workloads layer 90 provides examples of functionality for which thecloud computing environment may be utilized. Examples of workloads andfunctions which may be provided from this layer include: mapping andnavigation 91; software development and lifecycle management 92; virtualclassroom education delivery 93; data analytics processing 94;transaction processing 95; and DHCP processes 96 described herein. Inaccordance with aspects of the invention, the DHCP processes 96workload/function operates to perform one or more of the processesdescribed herein.

FIG. 4 depicts a cloud computing node according to another embodiment ofthe present invention. In particular, FIG. 4 is another cloud computingnode which comprises a same cloud computing node 10 as FIG. 1. In FIG.4, the computer system/server 12 also comprises or communicates with aDHCP client 170, a DHCP server 160, and a DHCP relay agent 180, asdescribed in greater detail herein.

In accordance with aspects of the invention, the DHCP client 170, theDHCP server 160, and the DHCP relay agent 180 can be implemented as oneor more program code in program modules 42 stored in memory as separateor combined modules. Additionally, the DHCP client 170, the DHCP server160, and the DHCP relay agent 180 may be implemented as separatededicated processors or a single or several processors to provide thefunction of these tools. While executing the computer program code, theprocessing unit 16 can read and/or write data to/from memory, storagesystem, and/or I/O interface 22. The program code executes the processesof the invention.

By way of example, DHCP client 170 may be configured to send a DHCPrequest packet to a DHCP server 160 via a cloud computing environment50. As discussed with reference to FIG. 2, for example, cloud computingenvironment 50 may be the Internet, a local area network, a wide areanetwork, and/or a wireless network. In response to the DHCP server 160receiving the DHCP request packet, the DHCP server 160 allocates an IPaddress for the DHCP client 170.

In embodiments of the DHCP mechanism, DHCP server 160 may provide directsupport for multi-tenancy on the DHCP protocol using a tenant-specificDHCP option to carry tenant information. Therefore, unlike currentsystems which require operating system virtualization (e.g., each tenanthaving a DHCP server running in a separate LINUX namespace), the DHCPserver 160 can support overlapped IP address spaces. In fact, the DHCPserver 160 provides numerous advantages and technical solutions overknown OS virtualization for multi-tenancy, including addressinginter-operability between different encapsulation protocols formulti-tenant isolation, high scalability (e.g., not as computationallyintensive), and seamlessly supports the software defined networking(SDN) address allocation requirement. Further, in FIG. 4, a DHCP relayagent 180 may be used as an intermediary to relay messages between DHCPclient 170 and DHCP server 160 via the cloud computing environment 50.One of ordinary skill in the art would understand that in anotherembodiment, DHCP client 170 and DHCP server 160 may communicate directlywith each other without use of the DHCP relay agent 180.

The present invention may be a system, a method, and/or a computerprogram product. The computer program product may include a computerreadable storage medium (or media) having computer readable programinstructions thereon for causing a processor to carry out aspects of thepresent invention.

The computer readable storage medium can be a tangible device that canretain and store instructions for use by an instruction executiondevice. The computer readable storage medium may be, for example, but isnot limited to, an electronic storage device, a magnetic storage device,an optical storage device, an electromagnetic storage device, asemiconductor storage device, or any suitable combination of theforegoing. A non-exhaustive list of more specific examples of thecomputer readable storage medium includes the following: a portablecomputer diskette, a hard disk, a random access memory (RAM), aread-only memory (ROM), an erasable programmable read-only memory (EPROMor Flash memory), a static random access memory (SRAM), a portablecompact disc read-only memory (CD-ROM), a digital versatile disk (DVD),a memory stick, a floppy disk, a mechanically encoded device such aspunch-cards or raised structures in a groove having instructionsrecorded thereon, and any suitable combination of the foregoing. Acomputer readable storage medium, as used herein, is not to be construedas being transitory signals per se, such as radio waves or other freelypropagating electromagnetic waves, electromagnetic waves propagatingthrough a waveguide or other transmission media (e.g., light pulsespassing through a fiber-optic cable), or electrical signals transmittedthrough a wire.

Computer readable program instructions described herein can bedownloaded to respective computing/processing devices from a computerreadable storage medium or to an external computer or external storagedevice via a network, for example, the Internet, a local area network, awide area network and/or a wireless network. The network may comprisecopper transmission cables, optical transmission fibers, wirelesstransmission, routers, firewalls, switches, gateway computers and/oredge servers. A network adapter card or network interface in eachcomputing/processing device receives computer readable programinstructions from the network and forwards the computer readable programinstructions for storage in a computer readable storage medium withinthe respective computing/processing device.

Computer readable program instructions for carrying out operations ofthe present invention may be assembler instructions,instruction-set-architecture (ISA) instructions, machine instructions,machine dependent instructions, microcode, firmware instructions,state-setting data, or either source code or object code written in anycombination of one or more programming languages, including an objectoriented programming language such as Smalltalk, C++ or the like, andconventional procedural programming languages, such as the “C”programming language or similar programming languages. The computerreadable program instructions may execute entirely on the user'scomputer, partly on the user's computer, as a stand-alone softwarepackage, partly on the user's computer and partly on a remote computeror entirely on the remote computer or server. In the latter scenario,the remote computer may be connected to the user's computer through anytype of network, including a local area network (LAN) or a wide areanetwork (WAN), or the connection may be made to an external computer(for example, through the Internet using an Internet Service Provider).In some embodiments, electronic circuitry including, for example,programmable logic circuitry, field-programmable gate arrays (FPGA), orprogrammable logic arrays (PLA) may execute the computer readableprogram instructions by utilizing state information of the computerreadable program instructions to personalize the electronic circuitry,in order to perform aspects of the present invention.

Aspects of the present invention are described herein with reference toflowchart illustrations and/or block diagrams of methods, apparatus(systems), and computer program products according to embodiments of theinvention. It will be understood that each block of the flowchartillustrations and/or block diagrams, and combinations of blocks in theflowchart illustrations and/or block diagrams, can be implemented bycomputer readable program instructions.

These computer readable program instructions may be provided to aprocessor of a general purpose computer, special purpose computer, orother programmable data processing apparatus to produce a machine, suchthat the instructions, which execute via the processor of the computeror other programmable data processing apparatus, create means forimplementing the functions/acts specified in the flowchart and/or blockdiagram block or blocks. These computer readable program instructionsmay also be stored in a computer readable storage medium that can directa computer, a programmable data processing apparatus, and/or otherdevices to function in a particular manner, such that the computerreadable storage medium having instructions stored therein comprises anarticle of manufacture including instructions which implement aspects ofthe function/act specified in the flowchart and/or block diagram blockor blocks.

The computer readable program instructions may also be loaded onto acomputer, other programmable data processing apparatus, or other deviceto cause a series of operational steps to be performed on the computer,other programmable apparatus or other device to produce a computerimplemented process, such that the instructions which execute on thecomputer, other programmable apparatus, or other device implement thefunctions/acts specified in the flowchart and/or block diagram block orblocks.

The flowchart and block diagrams in the Figures illustrate thearchitecture, functionality, and operation of possible implementationsof systems, methods, and computer program products according to variousembodiments of the present invention. In this regard, each block in theflowchart or block diagrams may represent a module, segment, or portionof instructions, which comprises one or more executable instructions forimplementing the specified logical function(s). In some alternativeimplementations, the functions noted in the block may occur out of theorder noted in the figures. For example, two blocks shown in successionmay, in fact, be executed substantially concurrently, or the blocks maysometimes be executed in the reverse order, depending upon thefunctionality involved. It will also be noted that each block of theblock diagrams and/or flowchart illustration, and combinations of blocksin the block diagrams and/or flowchart illustration, can be implementedby special purpose hardware-based systems that perform the specifiedfunctions or acts or carry out combinations of special purpose hardwareand computer instructions.

FIG. 5 is a frame format for a tenant-specific DHCP option in accordancewith aspects of the present invention. More specifically, FIG. 5 depictsa tenant-specific DHCP option frame format 100 for carrying tenantinformation. The tenant-specific DHCP option frame format 100 includes avariety of fields, including, but not limited to option 110, length 120,transport agent 130, tenant ID 140, and virtual network ID 150. Option110 is a unique value in DHCP options. Length 120 is a total number ofbytes of remaining fields. Transport agent 130 is an encoding value usedto denote the overlay protocol type that is used for tenant isolation,e.g., VLAN, VXLAN, DOVE, NVGRE, STT, etc. Tenant ID 140 is a universallyunique identifier (UUID) used to identify a tenant. Finally, virtualnetwork ID 150 denotes a virtual network, which is an abstract of a L2segment or broadcast domain.

A tenant may be joined to multiple virtual networks. The tenant-specificDHCP option frame format 100 is an indicator for a DHCP server toallocate an IP address on associated address space to that tenant.Therefore, a single DHCP server can serve a plurality of tenants, andeach tenant can have its own IP address pool for allocation. The poolsin different tenants are totally independent, and can be overlapped. Thetenant-specific option frame format 100 can be added to a DHCP header bya DHCP relay agent. In embodiments, the tenant-specific option is asub-option in DHCP relay agent information option (option 82, RFC 3046).Therefore, implementation will add a sub-option in the option 82 toinclude the tenant-specific option frame format 100.

Flow Diagram

FIGS. 6-8 show exemplary flows (or swim lane diagrams) for performingaspects of the present invention. The steps of FIGS. 6-8 may beimplemented in the environment of FIGS. 1 and 4, for example. As notedabove, the flowchart(s) illustrate the architecture, functionality, andoperation of possible implementations of systems, methods, and computerprogram products as already described herein in accordance with thevarious embodiments of the present invention. The flowchart and blockdiagrams in the Figures illustrate the architecture, functionality, andoperation of possible implementations of systems, methods and computerprogram products according to various embodiments of the presentinvention. In this regard, each block in the flowchart or block diagramsmay represent a module, segment, or portion of code, which comprises oneor more executable instructions for implementing the specified logicalfunction(s). It should also be noted that, in some alternativeimplementations, the functions noted in the block may occur out of theorder noted in the figures. For example, two blocks shown in successionmay, in fact, be executed substantially concurrently, or the blocks maysometimes be executed in the reverse order, depending upon thefunctionality involved. It will also be noted that each block of theblock diagrams and/or flowchart illustration, and combinations of blocksin the block diagrams and/or flowchart illustration, can be implementedby special purpose hardware-based systems that perform the specifiedfunctions or acts, or combinations of special purpose hardware andcomputer instructions.

FIG. 6 depicts an exemplary flow (swim diagram) for a DHCP packetprocessing in accordance with aspects of the present invention. Morespecifically, FIG. 6 shows a tenant-specific option added to the DHCPheader by a DHCP relay agent. Since a network virtualization edge (NVE)is an edge of the overlay network, it is easy to derive the encodingvalue of the transport agent in the tenant specific option. A virtualnetwork identifier (VNID) can be derived from a virtual access point(VAP) to which the DHCP client connects. The VAP is a logical connectionpoint on the NVE for connecting a tenant system to a virtual network.VAPs can be physical ports or virtual ports identified through logicalinterface identifiers, such as VLAN ID or internal vSwitch Interface IDconnected to a virtual machine (VM). The tenant ID in thetenant-specific option can be derived through the VNID by consulting thelocal cache or remote database in NVA that consists of the mappingbetween VNID and tenant ID.

In current DHCP relays, for each L2 segment it serves, a gateway IPinterface is needed, on which DHCP client packets on that L2 segmentwill be received. Therefore, in current DHCP systems, upon receiving aDHCP message from a DHCP client, the IP address of the IP interface willbe filled in the GIADDR field of the DHCP packet if it is zero, and theDHCP message is sent to the DHCP server. In other words, the GIADDR isadded by the first DHCP relay agent. The DHCP server will use the GIADDRto allocate the IP address and other network parameter to the DHCPclient. The DHCP server will send a corresponding DHCP relay message toa DHCP relay agent identified by the GIADDR. The DHCP relay agent isdesigned to send the DHCP reply message to the directly connected DHCPclients—the clients in the same L2 segment as the IP interface of theDHCP relay agent identified by the GIADDR.

In contrast, as shown in FIG. 6, DHCP clients are running in the overlaynetwork, and the overlay networks of different tenants are isolated. TheDHCP server is designed to serve all the DHCP clients in differenttenant overlay networks. The DHCP server and DHCP relay agents willcommunicate through the underlay network. The GIADDR added by the DHCPrelay agent will be an underlay IP address of the relay agent. The DHCPserver will not use the GIADDR to allocate the IP address and othernetwork parameters to DHCP client. The DHCP server will use thetenant-specific option and other options to allocate the IP address andother network parameters to the DHCP client. The DHCP server will send acorresponding DHCP reply message to a DHCP relay agent identified by theGIADDR. The relay agent will use the VNID in tenant-specific option todeliver the DHCP reply message to the DHCP client accordingly.

More specifically, FIG. 6 depicts an exemplary flow or swim lane diagramfor a DHCP packet processing in accordance with aspects of the presentinvention. FIG. 5 includes the following actors: DHCP client 210 (anexample of DHCP client 170 described with regard to FIG. 4), DHCP relayagent 220 (an example of DHCP relay agent 180 with regard to FIG. 4),and DHCP server 230 (an example of DHCP server 160 described with regardof FIG. 4).

In FIG. 6, in the DHCP packet processing, at step 231, a DHCP client 210sends a DHCP_DISCOVER message to a DHCP relay agent 220. Then, at step232, the DHCP relay agent 220 sends a DHCP_DISCOVER with tenant specificoption message to DHCP server 230. In step 233, the DCHP server 230 thensends a DHCP_OFFER with tenant specific option message to DHCP relayagent 220. At step 234, DHCP relay agent 220 sends a DHCP_OFFER messageto DHCP client 210. Then, at step 235, DHCP client 210 sends aDHCP_REQUEST message to the DHCP relay agent 220. The DHCP relay agent220 sends a DHCP_REQUEST with tenant specific option message to DHCPserver 230, at step 236. At step 237, DHCP server 230 sends a DHCP_ACKwith tenant specific option message to DHCP relay agent 220. Finally, atstep 238, DHCP relay agent 220 sends a DHCP_ACK message to DHCP client210.

FIG. 7 depicts an exemplary flow for an address allocation processing inaccordance with aspects of the present invention. In FIG. 7, to enablemulti-tenant support in the novel DHCP mechanism of the depictedembodiment, the DHCP server supports two types of address spaces: globaladdress space and tenant address space. The global address space iscompatible with current DHCP methods in which a tenant-specific optionis not present in the DHCP packet. In the global address space ofcurrent DHCP methods, the IP address ranges cannot be overlapped;whereas, in contrast, in the technical solutions of the DHCP mechanismof the depicted embodiment of the present invention, each tenant has aspecific address pool in the tenant address space. The address range inthe DHCP mechanism of the depicted embodiment can be overlapped acrossdifferent tenant's address pool.

For example, in the DHCP mechanism shown in FIG. 7, if the DHCP_DISCOVERmessage does not include the tenant specific option, the DHCP serverperforms a known DHCP processing. Otherwise, if the DHCP_DISCOVERmessage includes the tenant specific option, the tenant specific optionis used to locate the tenant address space and IP range. The DHCP serverlocates the address space corresponding to the tenant ID in thetenant-specific option. Also, in FIG. 7, if the DHCP_DISCOVER messagehas a subnet selection option (option 118) or a link selectionsub-option (sub-option 5 in option 82), the DHCP server will allocate anaddress from that subnet. Otherwise, if the DHCP_DISCOVER message doesnot have a subnet selection option or a link selection sub-option, an IPrange is associated to a VNID, and the DHCP server will find the IPrange according to the VNID in the tenant specific option. Further, thenovel DHCP mechanism of the depicted embodiment can include a DHCPserver which uses a matching criteria or access control list (ACL) ruleson the tenant-specific option in the configuration to locate the tenantaddress space.

More specifically, in FIG. 7, in the address allocation processing, atstep 305, a DHCP server receives a DHCP request packet. At step 310, theprocesses and systems of the DHCP server determine whether the DHCPrequest (e.g., DHCP_DISCOVER) has a specific option. If the DHCP requestdoes not have a tenant specific option (i.e., NO), at step 315, the DHCPserver uses a global address space. Then, at step 320, known DHCPprotocol processing is performed by the DHCP server and the DHCP client,since there is no tenant specific option.

Alternatively, at step 310, if the DHCP request (e.g., DHCP_DISCOVER)does have a tenant specific option (i.e., YES), at step 325, an addressspace is chosen by the DHCP server according to the tenant specificoption field. Further, at step 330, a determination is made by the DHCPserver as to whether there is either a link selection (option 118) or asubnet selection option (opt 82 subopt 5) in the DHCP request. If thereis no link (i.e., NO) at step 345, an address is allocated for VNID bythe DHCP server. Alternatively, at step 330, if there is either a linkselection (option 118) or a subnet selection option (opt 82 subopt 5) inthe DHCP request (i.e., YES), then at step 335, there is a check by theDHCP server whether an available address in a requesting subnet. At step335, if there is an available address in the requesting subnet (i.e.,YES), at step 340, an address is allocated in the subnet by the DHCPserver. Alternatively, at step 335, if there is not an available addressin the requesting subnet (i.e., NO), at step 345, an address isallocated for VNID by the DHCP server.

FIG. 8 depicts an exemplary flow for a DHCP subnet selection support inaccordance with aspects of the present invention. In FIG. 8, in the DHCPsubnet selection support in accordance with aspects of the presentinvention, a DHCP client 410 sends a DHCP_DISCOVER message to a DHCPrelay agent 420 in step 441. When the DHCP relay agent 420 receives theDHCP_DISCOVER message, DHCP relay agent 420 locates the tenant addressspace according to the tenant ID in the tenant specific option andallocates an IP address in the intended subnet. As shown in FIG. 7, theDHCP relay agent 420 derives its VNID from an associated VAP. Then, inFIG. 8, at step 442, the DHCP relay agent 420 sends a query subnet ofVNIDx message to a network virtualization authority (NVA) 440 to inquireof the subnet configuration of that VNID. A reply for the subnet ofVNIDx is sent by the NVA 440 to the DHCP relay agent in step 443.Finally, at step 444, the DHCP_DISCOVER with tenant specific option andsubnet selection option 118 or option 82 with subopt 5 is sent to DHCPserver 430.

In FIG. 8, a DHCP subnet selection option (option 118, RFC3011) and alink selection in relay agent information option (option 82, suboption5, RFC3527) are used to communicate to a DHCP server on a desired subnetfrom which the DHCP clients expect to obtain their IP address.Therefore, the novel DHCP mechanism of the depicted embodiment can beeasily extended to these situations through NVA.

As shown in FIG. 8, a NVA can maintain the subnet configuration for eachVNID. In response to receiving each DHCP_DISCOVER packet from DHCPclient 410, the DHCP relay agent 420 derives its VNID from theassociated VAP. After that, the DHCP relay agent 420 sends a query toNVA 440 to inquire of the subnet configuration of that VNID. The subnetconfiguration, which is replied by NVA 440, is then filled in the DHCPpotion 118 or option 82—suboption 5. The subnet information is thencommunicated to DHCP server 430 together with the tenant-specificationoption. When DHCP server 430 receives the DHCP_DISCOVER packet, DHCPserver 430 locates the tenant address space according to tenant ID inthe tenant specific option and allocates an IP address in the intendedsubnet which is carried in the DHCP option 118 or option 82—suboption 5.

In embodiments, a service provider, such as a Solution Integrator, couldoffer to perform the processes described herein. In this case, theservice provider can create, maintain, deploy, support, etc., thecomputer infrastructure that performs the process steps of the inventionfor one or more customers. These customers may be, for example, anybusiness that uses technology. In return, the service provider canreceive payment from the customer(s) under a subscription and/or feeagreement and/or the service provider can receive payment from the saleof advertising content to one or more third parties.

As should now be understood by those of skill in the art, in embodimentsof the present invention, the DHCP mechanism provides numerousadvantages over current systems. These advantages include, but are notlimited to, providing direct support for multi-tenancy on DHCP protocoland removing the need of LINUX namespace OS-level virtualization tosupport multi-tenancy. In embodiments of the present invention, thistechnical solution is accomplished by formulating a tenant-specific DHCPoption to carry tenant information and improving an address allocationscheme on a DHCP server to prioritize IP address allocation on thetenant address space once tenant-specific option is detected in the DHCPpacket.

Also, both the DHCP client and the DHCP relay agent can addtenant-specific option. Moreover, in embodiments, an interoperabilityissue between different encapsulation protocols for multi-tenantisolation (e.g., VLAN, VXLAN, DOVE, NVGRE, STT, etc.) is alleviated.

Moreover, embodiments of the DHCP mechanism provide high scalability asthe number of tenants grows. For example, in current systems,OS-virtualization to support multi-tenancy increases computationalburden because each instance of a LINUX namespace requires additionalresources; whereas, in embodiments of the DHCP mechanism of the presentinvention, computational burden is reduced in comparison to OS-levelvirtualization. Further, in embodiments of the DHCP mechanism, a SDNaddress allocation requirement is seamlessly supported because each DHCPclient gets correct addresses belonging to its tenant and its connectedvirtual network.

In still further advantages to a technical problem, the systems andprocesses described herein provide a computer-implemented method formulti-tenancy support on a DHCP protocol, on a network. In this case, acomputer infrastructure, such as the computer system shown in FIGS. 1and 4 or the cloud environment shown in FIG. 2 can be provided and oneor more systems for performing the processes of the invention can beobtained (e.g., created, purchased, used, modified, etc.) and deployedto the computer infrastructure. To this extent, the deployment of asystem can comprise one or more of:

-   -   (i) installing program code on a computing device, such as        computer system shown in FIG. 1, from a computer-readable        medium;    -   (ii) adding one or more computing devices to the computer        infrastructure and more specifically the cloud environment; and    -   (iii) incorporating and/or modifying one or more existing        systems of the computer infrastructure to enable the computer        infrastructure to perform the processes of the invention.

The descriptions of the various embodiments of the present inventionhave been presented for purposes of illustration, but are not intendedto be exhaustive or limited to the embodiments disclosed. Manymodifications and variations will be apparent to those of ordinary skillin the art without departing from the scope and spirit of the describedembodiments. The terminology used herein was chosen to best explain theprinciples of the embodiments, the practical application or technicalimprovement over technologies found in the marketplace, or to enableothers of ordinary skill in the art to understand the embodimentsdisclosed herein.

What is claimed is:
 1. A computer program product comprising a computerreadable storage medium having program instructions embodied therewith,wherein the computer readable storage medium is not a transitory signalper se, the program instructions executable by a dynamic hostconfiguration protocol (DHCP) relay agent computing device to cause theDHCP relay agent computing device to: receive a DHCP packet; and inserta tenant-specific option information within the DHCP packet, wherein thetenant-specific option information is an indicator to a DHCP server toallocate an internet protocol address on an associated address spacespecific to a tenant in a multiple tenant cloud data center based onoverlay networks.
 2. The computer program product of claim 1, whereinthe tenant-specific option information is selected from at least one ofthe group consisting of: a transport agent field used to denote anoverlay protocol type that is used for tenant isolation; and a tenantidentification field used to uniquely identify the tenant.
 3. Thecomputer program product of claim 2, wherein the overlay protocol typeis selected from one of the group consisting of: a virtual local areanetwork (VLAN); virtual extensible local area network (VXLAN);distributed overlay virtual ethernet (DOVE); network virtualizationusing generic routing encapsulation (NVGRE); stateless transporttunneling (STT); and generic network virtualization encapsulation(GENEVE).
 4. The computer program product of claim 1, wherein thetenant-specific option information comprises a virtual networkidentification field used to denote a virtual network.
 5. The computerprogram product of claim 1, wherein the tenant-specific optioninformation is inserted in a DHCP header of the DHCP packet.
 6. Thecomputer program product of claim 1, wherein the DHCP packet is receivedat the DHCP relay agent computing device and the tenant-specific optioninformation is inserted within the DHCP at the DHCP relay agentcomputing device.
 7. The computer program product of claim 6, whereinthe DHCP packet with the tenant-specific option information istransmitted from the DHCP relay agent computing device to a DHCP server.8. The computer program product of claim 1, wherein the programminginstructions are further configured to transmit an internet protocol(IP) address to a DHCP client which corresponds with a tenantidentification field of the tenant-specific option information.
 9. Thecomputer program product of claim 8, wherein the IP address transmittedto the DHCP client corresponds with the tenant identification field ofthe tenant-specific option information and overlaps with an IP addressof a different independent tenant.
 10. The computer program product ofclaim 1, wherein the DHCP relay agent computing device runs on a networkvirtualization edge (NVE).
 11. The computer program product of claim 10,wherein the DHCP server uses access control list (ACL) rules on thetenant-specific option information to locate the associated addressspace specific to the tenant.
 12. A system comprising: a processor, acomputer readable memory and a computer readable storage mediumassociated with a dynamic host configuration protocol (DHCP) server;program instructions to receive a DHCP packet; program instructions todetermine that the DHCP packet comprises tenant-specific optioninformation; and program instructions to determine that the DHCP packetwith the tenant-specific option information has at least one of a linkselection sub-option and a subnet selection option, wherein thetenant-specific option information is an indicator to the DHCP server toallocate an internet protocol address on an associated address spacespecific to a tenant in a multiple tenant cloud data center based onoverlay networks, and the program instructions are stored on thecomputer readable storage medium for execution by the processor via thecomputer readable memory.
 13. The system of claim 12, furthercomprising: determining that an address is available in a requestedsubnet when the DHCP packet is determined to have at least one of thelink selection sub-option and the subnet selection option; andallocating the address in the requested subnet when the address isavailable in the requested subnet.
 14. The system of claim 13, furthercomprising allocating an address for a virtual network identifier inresponse to a determination that the DHCP packet does not have at leastone of the link selection sub-option and the subnet selection option.15. The system of claim 14, further comprising allocating an address fora virtual network identified in response to a determination that theaddress is not available in the requested subnet.
 16. The system ofclaim 14, further comprising program instructions to allocate a globaladdress space in response to a determination that the received DHCPpacket is devoid of the tenant-specific option information.
 17. Acomputer program product comprising a computer readable storage mediumhaving program instructions embodied therewith, wherein the computerreadable storage medium is not a transitory signal per se, the programinstructions executable by a dynamic host configuration protocol (DHCP)relay agent computing device to cause the DHCP relay agent computingdevice to: insert multi-tenancy information within a DHCP packet; andlocate an associated address space specific to a tenant by using accesscontrol list (ACL) rules in the multi-tenancy information, wherein themulti-tenancy information including tenant-specific option informationindicating to a DHCP server to allocate an internet protocol address onthe associated address space specific to the tenant in a multiple tenantcloud data center.
 18. The computer program product of claim 17, whereinthe multi-tenancy information is selected from at least one of the groupconsisting of: a transport agent field used to denote an overlayprotocol type that is used for tenant isolation; a tenant identificationfield used to uniquely identify the tenant; and a virtual networkidentification field used to denote a virtual network, and thetenant-specific option information comprises a transport agent fieldused to denote an overlay protocol type that is used for tenantisolation, and the overlay protocol type is selected from one of thegroup consisting of: a virtual local area network (VLAN); virtualextensible local area network (VXLAN); distributed overlay virtualethernet (DOVE); network virtualization using generic routingencapsulation (NVGRE); stateless transport tunneling (STT); and genericnetwork virtualization encapsulation (GENEVE).
 19. The computer programproduct of claim 17, wherein the program instructions further cause theDHCP relay agent computing device to transmit an internet protocol (IP)address to a DHCP client which corresponds with a tenant identificationfield of the tenant-specific option information, and the IP addresstransmitted to the DHCP client corresponds with the tenantidentification field of the tenant-specific option information andoverlaps with an IP address of a different independent tenant.
 20. Thecomputer program product of claim 17, wherein the program instructionsfurther cause the DHCP relay agent computing device to: configure afirst field of a tenant-specific DHCP option frame format to denote anoverlay protocol type that is used for tenant isolation in overlayvirtual networks; configure a second field of the tenant-specific DHCPoption frame format to uniquely identify a tenant in the multiple tenantcloud data center; and configure a third field of the tenant-specificDHCP option frame format to denote a virtual network of the overlayvirtual networks, wherein the second field is used by the DHCP server tolocally scope an address range to an address space of the tenant.